Critical Analysis & Reasoning Skills Practice Questions: 16 | Critical Analysis & Reasoning Skills for MCAT PDF Download

A land bridge refers to exposed land that connects two separate landmasses when the sea recedes. Currently, one existing land bridge is the Sinai Peninsula, which links the Middle East to North Africa. Another land bridge is found in Central America, connecting North and South America.

Throughout history, there have been numerous land bridges. For example, there was a bridge connecting the British Isles to the European continent, as well as one between Spain and Morocco at the Straits of Gibraltar. Japan was also connected to China and Korea by land bridges. Perhaps one of the most well-known land bridges was the Bering Land Bridge, also known as Beringia, which connected Alaska to Siberia across what is now the Bering Strait.

Although the Bering Land Bridge was relatively short in length, it would have been possible to drive across it in about an hour if it still existed today. This land bridge emerged during the Ice Age when large ice sheets covered significant portions of Europe and America. Due to the massive amounts of water stored in the ice sheets, the sea level dropped significantly, possibly by as much as 400 feet. As a result, land areas like the Bering Land Bridge became visible.

During this time, the northern hemisphere's ecology resembled the Mammoth Steppe, a cold and arid land characterized by grasses, sedges, and tundra vegetation. It was home to various large grazing animals, including reindeer, bison, musk oxen, and the predators such as lions that preyed upon them. The Mammoth Steppe also housed large camels, giant short-faced bears, and woolly mammoths.

The Bering Land Bridge may have had a slightly higher moisture content compared to other parts of the Mammoth Steppe since it was bordered by the ocean to the north and south and influenced by ocean breezes. Many of the animals from the Mammoth Steppe used this land bridge as a pathway for migration from east to west and vice versa. Eventually, humans followed these animal herds from Asia to North America.

Ethnologists and geologists generally support the theory that humans used the Bering Land Bridge to populate the Americas, which lacked evidence of human habitation until approximately 24,000 years ago. They base their conclusions on shared religions, similar types of housing and tools, and unique methods of food preservation and preparation observed among the people of coastal Siberia and coastal Alaska.

However, there are Native Americans who dispute the land bridge theory. They argue that it contradicts their traditional teachings regarding the origins of their people. Additionally, they believe it undermines the concept of being truly "native" to the North American continent.

Around 12,000 years ago, the waters returned, submerging the land bridge, and today, with global warming, the sea level continues to rise steadily. Standing on the shores of the Seward Peninsula, it is challenging to imagine walking across to Russia. However, looking at a map, the proximity of the land borders gives the impression that the continents are almost touching. Just a momentary holding back of the waters, similar to the story of Moses in The Ten Commandments, allows one to visualize a Pleistocene hunter pursuing a woolly mammoth across the land bridge to the untamed continent beyond.
Q.1. Which of the following best describes a land bridge?
(a) A submerged pathway between two continents.
(b) A connection between landmasses exposed when the sea recedes.
(c) A bridge constructed to link two separate land areas.
(d) A formation created by volcanic activity connecting islands.

Correct Answer is Option (b)
The passage defines a land bridge as land exposed when the sea recedes, connecting one landmass to another. It is a natural occurrence rather than a man-made structure, making choice B the correct answer.

Q.2. What evidence supports the theory that humans used the Bering Land Bridge to populate the Americas?
(a) Fossils of early human settlements in Alaska.
(b) Similar housing and tools found in coastal Siberia and coastal Alaska.
(c) Oral traditions passed down by Native American tribes.
(d) Geological studies of the Bering Strait.

Correct Answer is Option (b)
The passage states that ethnologists and geologists support the theory of humans using the Bering Land Bridge based on evidence such as shared religions, similar houses and tools, and unique methods of cleaning and preserving food found among the people of coastal Siberia and coastal Alaska. Therefore, choice B is the correct answer.

Q.3. Why do some Native Americans dispute the land bridge theory?
(a) They believe it contradicts scientific evidence.
(b) It challenges their traditional teachings about their origins.
(c) They have found evidence of alternative migration routes.
(d) The theory undermines the importance of their culture.

Correct Answer is Option (b)
The passage mentions that some Native Americans dispute the land bridge theory because they believe it contradicts their traditional teachings about the origins of their people. They are concerned that it undermines the notion of being truly "native" to the North American continent. Thus, choice B is the correct answer.

Q.4. How did the Bering Land Bridge form?
(a) It was built by ancient civilizations.
(b) Volcanic activity created the land bridge.
(c) Melting ice sheets caused the sea level to drop, revealing the land bridge.
(d) Tectonic plate movement connected Alaska to Siberia.

Correct Answer is Option (c)
According to the passage, the Bering Land Bridge formed during the Ice Age when enormous ice sheets covered parts of Europe and America. The sea level dropped significantly, possibly due to the massive amounts of water stored in the ice sheets. As a result, landmasses such as the Bering Land Bridge became visible. Therefore, choice C is the correct answer.

Q.5. Which factor challenges the visualization of the Bering Land Bridge today?
(a) Increased global warming causing the sea level to rise.
(b) The presence of a current land bridge between Alaska and Siberia.
(c) The absence of historical records about the land bridge.
(d) Geological instability in the Bering Strait region.

Correct Answer is Option (a)
The passage mentions that the waters returned around 12,000 years ago, submerging the Bering Land Bridge. Currently, global warming contributes to a steady rise in sea levels. Therefore, it becomes challenging to imagine walking across the Bering Land Bridge today due to the increased sea level caused by global warming. Thus, choice A is the correct answer.